Abstract

A new vibroviscometer is proposed, and it was fabricated in order to prove its feasibility. The viscometer consists of a triangular bimorph transducer and a circular thin plate. The bimorph transducer consists of two piezoelectric plates and a metal shim plate, and the shim plate is sandwiched in between the piezoelectric plates so that two pairs of piezoelectric–metal‐plate (unimorph) transducers can be used separately as driving and detecting transducers. The circular plate is adhered on the acute tip of the triangular transducer at a right angle to the transducersurface. As the measurement procedure, only the circular plate driven by one unimorph transducer is immersed in the liquid and the output of the other unimorph transducer is monitored to be compared with the driving signal. It was found that the difference in the electrical phase between the driving and the monitored signals appears to be in proportion to the viscosity of liquids and that the difference remarkably appears at the range of the antiresonance frequency between the first and the second resonance frequency of the triangular bimorph. The reason for this is that the viscosity of the liquid exerts a retarding force on the plate. As for the results of the experiments regarding the frequency characteristics, the temperature characteristics, and the measurement of the viscosity for many liquids, it was proved that this phase difference method using the triangular bimorph can be used successfully for precise measurements of the viscosity.